Phuket Prison Commander Rapin Nichanon says that those ladyboys who have undergone gender reassignment are categorised as females at the prison.
Those who still have male sexual organs are kept with the male inmates, he told Bangkok Post journalist Chaiyot Yongcharoenchai.
''We treat them no differently than any other male inmates,'' the commander said.
In several visits inside Phuket Prison, and in interviews with former prisoners, Phuketwan has been told of ladyboys who commit crimes - most often petty theft - just so they can return to the jail.
Some of them feel more comfortable on the inside than on the outside, where prejudice and discrimination can be more obvious.
A letter sent by a ladyboy currently serving time in Phuket Prison told friends: ''I am writing to let you know that I am doing great. Even though 10 years sounds like a long time . . . I am enjoying every moment of my time here.''
Commander Rapin told the Bangkok Post: ''The male inmates may think that ladyboys are the closest thing to a woman they can find in prison, and the number of male inmates is much higher than the number of ladyboy inmates.
''For this reason, ladyboy inmates are given a lot of attention by male inmates. We never encourage this kind of activity but we don't stop it from happening either since it is human nature and it is not against the law.
''We have no policy to separate ladyboy inmates from male inmates. First of all, we don't have enough room to do that.
''Our prison can handle 800 prisoners, but we currently house around 2000. I also think the prisoners prefer to live this way.''
There are 1798 male inmates in Phuket Prison of whom 87 are ladyboys. Only two have had gender reassignment surgery, and are thus categorised in the prison as females.
Phuket Prison has a good reputation as a ''white'' jail, free from drugs, illegal telephones and weapons, while Commander Rapin's reputation is as a reformer.
As a holiday island, Phuket has a particular affinity with ladyboys, who attract tourists to cabaret shows and are a focus of attention in Phuket's west coast tourism hub, Patong.
Everyone in Patong who works after hours is required to register for a color-coded card, says the Bangkok Post. Blue cards are used to identify male workers, and pink cards for females and ladyboys.
Sompol ''Vicky'' Sitthiwatch of the Phuket-based Andaman Power group said: ''The color-coded cards are called 'passports' by people in the industry.
''People who have it are legal, while those who don't have may face fines of up to 1000 baht.
''With all this discrimination from people in society, I believe this is why ladyboys feel safer in prison.''
Andaman Power is a Phuket-based group working directly with the lesbian, gay, bisexual and transgender community. The group helps educate LGBT people who work in Phuket's night entertainment venues about safe sex, regular health checks and medical treatment.